Here I am sharing two cool features that most of all users in Facebook wants.. but FB hasn't cared or even thought about providing those features.. Those are Unfriend and Dislike options..
1. Unfriend Finder:
Unfriend Finder is a UserScript that requires installation via Greasemonkey. Once installed, it will integrate with Facebook and synchronize your current friends list with it to determine what friends you currently have and if those friends remove (unfriend) you. It will also notify you about certain scenarios; such as when your requested friends have accepted or declined you, when a current friend has deactivated or reactivated their profile and much more. Unfriend Finder can be installed on Firefox, Google Chrome, Safari and Opera.
2. Dislike Button:Facebook is known for it's signature feature 'LIKE'. There is option for liking everything like a post, picture, page, link, video and even webpages. It has been a high demand by FB users to have a Dislike Button too as many stuffs are not suitable to Like and they want to publicly Dislike it rather than commenting "dislike".
NOTE:These two features will take space on your facebook page and ads will be shown. So better not to install them if you don't want to bare those annoying ads. [You can always use AdBlock+ and enable it on Facebook to stop executing all ads.]